Hyaluronic acid has many medical uses, and various HARCs have been developed. The term HARC includes hyaluronic acid itself (including HA from living sources such as avian or bacterial sources), as well as hyaluronic acid salts and derivatives of the foregoing, including polymerized gels, cross-linked gels, and derivatized hyaluronic acid.
HARCs may be administered by themselves, for example to provide relief from arthritis. They also may be mixed with anti-inflammatory steroids. Lyons US2006/0141049 discloses pharmaceutical compositions containing triamcinolone acetonide and hyaluronate. Yu et al., Osteoarthritis and Cartilage vol. 12, Supp. B, P350 at page S144 (2004) discloses an in vitro evaluation of hylan G-F 20 diluted with a corticosteroid (triamcinolone acetonide) suspension.
When used in a medical product HARCs typically are sterilized by heating, autoclaving, chemical treatment or filtration. Often it is important to maintain the viscoelastic properties of the HARC. Sterilization techniques may alter viscoelastic properties or make it difficult to control or maintain the stability of those properties. Sterilization may decrease the shelf life of the product.
In some cases, HARCs are heat sterilized before forming a steroid/HARC mixture. Sterility of the final mixture may be achieved by filtration of the steroid solution before it is mixed with the HARC.